The present invention relates generously to an improved heart valve prosthesis, and more particularly to such a prosthesis device which may be implanted to replace the defective natural heart valve. The improved prosthesis device of the present invention employs a pair of occluder means, each in the form of a flat plate, both functioning hemodynamically through periodic opening and closing motion which is created through normal pumping action of the heart.
The present invention is a modification of that certain heart valve prosthesis disclosed and claimed in U.S. Pat. Nos. 4,692,165, Bokros and 4,822,353, Bokros, with the structure of the present invention utilizing modified forms of pivot means, occluder stop means, internal configurations for the annular body or ring, all of which combine to provide modified forms of flow characteristics through the valve prosthesis. The structural configuration involved in the device of the present invention is designed to improve the flow dynamics and reduce areas of statis, and if possible, significantly reduce if not eliminate the formation of eddies in the flow pattern through the valve.
Prosthetic heart valves function essentially as check valves. Blood flow which occurs as a result of the natural pumping action of the heart causes periodic opening of the occluder means, with the system pressure closing the occluder means during periods of diastole when in the aortic position or during periods of systole when in the atrio-ventricular position.
A variety of prosthetic heart valves have been proposed and utilized in the past. Certain of these prosthetic devices have employed a caged ball arrangement which also function and control blood flow in response to the normal pumping action of the heart. Other heart valve prostheses have employed occluders in the form of either a round disc or a pair of semi-circular and semi-elliptical plates. The latter are normally referred to as bi-leaflet valves. While various materials of construction have been employed in the past, the more recently utilized heart valve prostheses have been fabricated essentially from pyrolytic carbon. The improved prosthetic heart valve of the present invention is a bi-leaflet valve fabricated from pyrolytic carbon.
Bi-leaflet heart valves normally employ pivot means to appropriately guide and otherwise control the motion of the leaflets through their transition from open disposition to closed disposition. In addition, means have been provided to control or limit the extent of motion to which the leaflets are subjected during opening and closing, thereby providing an arrangement wherein the motion of the individual leaflets is carefully guided, controlled, limited, and maintained.
It is known that blood components including those cells normally found in human blood are extremely fragile and delicate, and that these cells can be damaged and/or destroyed when subjected to unusual mechanical forces. Thus, care must be taken in order to control the nature of the forces created due to the occurrence of relative motion between the leaflets and the annular body. For example, reduction of the occurrences of rubbing contact between stationary and moving surfaces is of importance when such contact is likely to cause mechanical damage to the components or cells present in blood. The design and configuration of the heart valve prosthesis of the present invention is such that care has been taken to reduce the creation of zones or areas where blood passing through the device is exposed to substantial mechanical forces. In addition to damage due to mechanical forces, it has been found that constituents of human blood are subject to damage whenever any quantity of blood is retained or held in an area or zone of stasis or stagnation within a prosthesis. The design and configuration of the heart valve prosthesis of the present invention is such that areas of stasis are reduced, if not entirely eliminated.